Triclocarban (TCC) has recently been described as a new type endocrine disruptor substance (EDS). Human exposures to TCC are quite broad since this compound is a common additive to personal care products for its antimicrobial properties. In vitro and in vivo studies show that TCC augments the action of sex steroid hormones on adult target tissues with no or little bioactivity on its own. In vivo studies demonstrate that a diet supplemented with TCC (0.25% w/w for ten days) increases accessory sex organ growth by 50 - 200% when administered to adult male rats. Furthermore, circulating TCC levels attained are similar to levels measured in humans following normal daily use of common personal care products. However, limited information is available regarding its potential impact on reproductive health during in utero and/or neonatal exposure. These time periods are the most important and sensitive intervals for sexual differentiation and sex organ development. There is increasing concern over embryonic determinants of adult health and the present proposal is designed to investigate placental transfer and effect of dietary TCC exposure on a rodent dam. Specifically, this application proposes to quantify placental transfer and determine the relative adverse effects of exposure to this novel EDS on reproductive tract development at two different sensitive periods in the rodent model. We hypothesize that exposure to TCC in both exposure periods will accelerate or accentuate the maturation of reproductive tract in both males and females. The results from the proposal will provide pivotal information on the adverse effects of TCC on sexual development and foundation information for new avenues of exploration into the etiology of many sex hormone associated disorders that have not been explained by investigations of conventional EDS. PUBLIC HEALTH RELEVANCE: The recent finding that TCC has novel endocrine disruptor properties raises the possibility that daily exposures during pregnancy to TCC may have a wide range of adverse health effects. Animal studies indicate that accessory sex organs are enlarged by TCC exposure and suggest a potential adverse effect on sexual differentiation and organ development. This proposal will address the increasing concern over embryonic determinants of adult health resulting from environmental factors and provide guidance for future investigations of the health risk from in utero and neonatal TCC exposure.